Comprehensive assessments of adolescent personality, carried out independently for early and late adolescence, in three longitudinal samples (born within the decade 1920-1930) provide a unique opportunity to study prospectively, in a group of 164 participants, personality antecedents of cigarette smoking (age of initiation, persistent level, and successful cessation). Data on current smoking practices, and complete smoking histories, were obtained in adulthood. The predictability of smoking precocity and level is to be evaluated for 104 individual characteristics, 19 adolescent personality dimensions, and an index of psychological health (using gamma coefficients). Whether these personality dimensions and psychological health can discriminate between heavy smokers and nonsmokers will be determined (by stepwise discriminant analysis). The same procedure will predict, among regular smokers, those who are successful smoking "quitters" and those who continue to smoke. To determine the generality of the results to a comtemporary cohort, these studies will be repeated for a sample of offspring of the original longtudinal samples. Identical adolescent personality data are now available for them, and smoking information will be obtained when they are about 24-28 years old. The estimated new sample size is 160. Only partial correspondence between the two sets of results is expected; discrepancies will be interpreted in light of the different cultural climates in which cigarette smoking began for the two generations. The results should prove useful in suggesting changes in current anti-smoking programs. Also, these studies may indicate how better to reach the current adolescent generation in which smoking is on the rise, and new directions for persuading chronic smokers, of whatever generation, to join the ever-growing company of "quitters".